This application claims the priority benefit of Japanese application serial no. 2001-270335, filed on Sep. 6, 2001.
1. Field of Invention
The present invention relates to a method and an apparatus for measuring the concentrations of the components of a fluid. More particularly, the present invention relates to a method and an apparatus capable of rapidly and continuously measuring the concentrations of the components of a fluid.
2. Description of Related Art
In various processes of gas production or semiconductor fabrication, it is quite important to be able to control the concentrations of the components of a gas/liquid fluid in real time with a low cost. For example, in a gas separation apparatus, the concentrations of the gas components at its outlet varies as the one at its inlet varies. Therefore those concentrations have to be measured continuously in order to adjust the conditions for gas separation and to control the concentrations of the components of the gas product. Similarly, the concentrations of the components of a fluid need to be measured continuously in other applications that requires controlling the concentrations of gas/liquid components. Particularly, in the field of semiconductor process, the performance of a semiconductor product is relatively dependent on the concentrations of impurities in a high-purity gas being used. If the high-purity gas is contaminated by undesired components or varies in its composition, the yield of the semiconductor products will be reduced significantly.
In the prior art, a component with a relatively high concentration in a gas are analyzed by using gas chromatography (GC) or non-dispersive infrared (NDIR) spectroscopy. However, the GC method can only perform non continuous measurement and can not be used for continuous measurement in real time. Moreover, since the GC method uses a separating column to separate each component of a gas sample, the gas sample to be measured has to be mixed with a carrier gas like helium (He) and therefore can not be reused after the measurement. Consequently, the so-called xe2x80x9cin-line monitoringxe2x80x9d can not be implemented by using the GC method.
On the other hand, the NDIR spectroscopy can be used for continuous monitoring in real time and is a method frequently used for in-line monitoring. However, since a window made from an IR-transparent material, such as quartz, has to be disposed on the cell of an IR spectrometer, the measuring apparatus for measuring a high-pressure gas is quite bulky. Moreover, since the components to be measured must be IR active, the IR method has the disadvantage that it can not be used to monitor the components IR inactive such as nitrogen (N2) and oxygen (O2), which easily leak into the cell and highly require to be monitored.
Accordingly, this invention provides a method and an apparatus capable of measuring the concentrations of the components of a fluid in real time and implementing in-line monitoring. The method and the apparatus can be used to measure a high-pressure gas or to measure the concentrations of various components in a fluid.
In a method for measuring the concentrations of the components of a fluid disclosed in this invention, a fluid sample is conducted through a measuring tube having a small aperture with a constant diameter in a fluid flow path. The pressure difference between the upstream and the downstream of the small aperture and the flow rate at the downstream of the small aperture are measured to determine the concentrations of the components of the fluid.
In another method for measuring the concentrations of the components of a fluid disclosed in this invention, the fluid sample is conducted through a measuring tube having a small aperture with a constant diameter in a fluid flow path. The pressure difference between the upstream and the downstream of the small aperture is controlled to be constant and the flow rate at the downstream of the small aperture is measured to determine the concentrations of the components of the fluid.
In the two methods of this invention mentioned above, at least one of the temperatures of the fluid sample, the measuring tube and the circumstance of the measuring tube can be measured to correct the concentrations of the components just being determined. Besides, it is also feasible to control at least one of the temperatures of the fluid sample, the measuring tube and the circumstance of the measuring tube to be constant.
An apparatus for measuring the concentrations of the components of a fluid disclosed in this invention comprises a measuring tube, a differential pressure gauge, a flow meter and a calculating device. The measuring tube has a small aperture with a constant diameter is in a fluid flow path. The differential pressure gauge is used for measuring the pressure difference between the upstream and the downstream of the small aperture. The flow meter is used for measuring the flow rate of the fluid at the downstream of the small aperture. The calculating device is used to calculate the concentrations of the components of the fluid from the pressure difference and the flow rate being measured.
Another apparatus for measuring the concentrations of the components of a fluid described in this invention comprises a measuring tube, a differential pressure controller, a flow meter and a calculating device. The measuring tube has a small aperture with a constant diameter in a fluid flow path. The differential pressure controller is used for controlling the pressure difference between the upstream and the downstream of the small aperture to be constant. The flow meter is used for measuring the flow rate of the fluid at the downstream of the small aperture. The calculating device is used for calculating the concentration of the component of the fluid sample from the constant pressure difference and the flow rate being measured.
The two apparatus of this invention each may further comprises a temperature measuring device for measuring at least one of the temperatures of the fluid sample, the measuring tube and the circumstance of the measuring tube, while the calculating device is capable of correcting the concentrations of the components based on the temperature being measured. Besides, the apparatus may include a temperature controller for controlling at least one of the temperatures of the fluid sample, the measuring tube and the circumstance of the measuring tube.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.